A magnetic recording disk of the particulate media type is characterized by a substrate having a coating of magnetic particles dispersed in an organic binder. The organic binder typically includes various polymers, such as a blend of epoxy and phenolic resins, solvents, dispersants to aid in the dispersion of the magnetic particles in the binder, and flow agents to facilitate the subsequent spin coating of the disk substrate. After the disk has been cured, a liquid lubricant is then applied to the coating to facilitate movement of the read/write head over the disk surface during start and stop operations of the disk file. Some particulate magnetic recording disks also incorporate load-bearing particles, such as alumina (Al.sub.2 O.sub.3), into the organic binder to increase the durability of the coating and prevent damage to the disk from impact from the read/write head. While the most common type of particulate recording disk is for horizontal recording, in which the magnetic axes of the particles are aligned parallel to the plane of the disk, particulate disks may also be fabricated for vertical recording by having the magnetic axes of the particles oriented perpendicular to the plane of the disk.
The use of a liquid lubricant on the disk presents disadvantages. If the disk is under-lubricated there may be too much friction between the disk and the read/write head, which results in increased wear to the disk and head. On the other hand, if the disk is over-lubricated, it becomes difficult for the head to break loose from the disk at start-up of the disk file.
The use of alumina or other load-bearing particles into the coating likewise presents disadvantages. Because the alumina lends nonhomogeneity to the coating, there is an increased number of magnetic defects, such as missing bits. Also, because the alumina particles are located close to the disk surface in order to accomplish their load bearing function, they are often forced out of the disk surface and thus create disk asperities. If it is desired to fly the head at a relatively low flying height, then the presence of asperities requires an additional step in the fabrication process, namely a smoothing or burnishing of the disk surface by a burnishing head which flies at a substantially reduced flying height to shear off the asperities. Despite the removal of the asperities, the alumina particles often move out of the disk coating and above the flying height of the read/write head during operation, which can cause the head to crash into the disk surface.